1. Field of the Invention
The present invention relates generally to image sensors, and more particularly to an image sensor with embossing structures for minimization of cracking in a protective layer.
2. Background of the Invention
An image sensor converts an optical image into electrical signals. With development of computer and communication industries in recent years, advanced image sensors are widely used in various devices such as digital cameras, camcorders, PCSs (Personal Communication Systems), game machines, security cameras, medical micro cameras, and the like.
A MOS (metal oxide semiconductor) image sensor is driven by a simple driving method and may be implemented with various scanning methods. The MOS image sensor has a signal processing circuit integrated as a single chip for reduced product size. In addition, fabrication of the MOS image sensor using MOS process technologies ensures low manufacturing costs. Furthermore, the MOS image sensor has low power consumption for application in a product with limited battery capacity. Additionally with development of technology, the MOS image sensor has high resolution such that the MOS image sensor is increasingly used.
The MOS image sensor includes a pixel array region having a plurality of unit pixels and includes a peripheral circuit region having circuits for controlling and driving the plurality of unit pixels. The pixel array region includes a plurality of photoelectric conversion elements and a plurality of MOS transistors. The peripheral circuit region includes a plurality of MOS transistors. The pixel array region and the peripheral circuit region are integrated in a single substrate with the MOS transistors in such regions being simultaneously formed.
For increasing collection efficiency, lenses are formed for corresponding photoelectric conversion elements in the pixel array region. A protective layer of LTO (Low Temperature Oxide) is formed over the lenses. During packaging, the MOS image sensor may undergo thermal and mechanical stress. Such thermal and mechanical stress may cause a crack in the protective layer. The crack may extend from the peripheral circuit region to the pixel array region. Such a crack may adversely affect on the path of incident light with deterioration of optical characteristics of the MOS image sensor.